Remove other permissions if a user does not have read on a channel

src/Discord.Net/Models/User.cs

@@ -322,6 +322,8 @@ namespace Discord
 			var mask = ChannelPermissions.All(channel).RawValue;
 			if (BitHelper.GetBit(newPermissions, (int)PermissionsBits.ManageRolesOrPermissions))
 				newPermissions = ChannelPermissions.All(channel).RawValue;
+			else if (!BitHelper.GetBit(newPermissions, (int)PermissionsBits.ReadMessages))
+				newPermissions = ChannelPermissions.None.RawValue;
 			else
 				newPermissions &= mask;